1. Field of the Invention
The present invention relates to video-signal processing methods, programs of video-signal processing methods, recording media having recorded thereon programs of video-signal processing methods, and video-signal processing apparatuses. For example, the present invention can be applied to noise filters that reduce noise in video signals. According to the present invention, regions with extremely small noise levels are excluded from subjects of noise-level measurement. Thus, the accuracy of noise-level measurement car, be improved.
2. Description of the Related Art
In various video-signal processing apparatuses, noise is removed from video signals, for example, by an infinite impulse response (IIR) noise filter. Such a noise filter generates a correction signal by correcting the signal level of a noise signal component extracted from video signals, and subtracting the correction signal from the original video signals to reduce noise.
Thus, when the level of the correction signal is too large, blurring occurs at object boundaries, texture regions, or the like. Conversely, when the level of the correction signal is too small, noise is not suppressed sufficiently.
Thus, various video-signal processing apparatuses are configured so that the level of the correction signal can be changed by an operation by an operator. On the other hand, for example, Japanese Unexamined Patent Application Publication No. 2001-136416 proposes techniques for automatically setting the level of the correction signal on the basis of results of noise-level measurement.
However, existing methods are not practically sufficient to measure noise level accurately. Thus, it has been difficult to remove noise appropriately.